From 782d97efec66d743f87f28f1d040cdfacc380b1e Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Fri, 7 Jul 2017 07:44:49 -0500 Subject: mirror: Switch mirror_cow_align() to byte-based We are gradually converting to byte-based interfaces, as they are easier to reason about than sector-based. Convert another internal function (no semantic change), and add mirror_clip_bytes() as a counterpart to mirror_clip_sectors(). Some of the conversion is a bit tricky, requiring temporaries to convert between units; it will be cleared up in a following patch. Signed-off-by: Eric Blake Reviewed-by: John Snow Reviewed-by: Jeff Cody Reviewed-by: Kevin Wolf Signed-off-by: Kevin Wolf --- block/mirror.c | 63 ++++++++++++++++++++++++++++++++++------------------------ 1 file changed, 37 insertions(+), 26 deletions(-) (limited to 'block') diff --git a/block/mirror.c b/block/mirror.c index a41ef25eee..0378bd2977 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -176,6 +176,15 @@ static void mirror_read_complete(void *opaque, int ret) aio_context_release(blk_get_aio_context(s->common.blk)); } +/* Clip bytes relative to offset to not exceed end-of-file */ +static inline int64_t mirror_clip_bytes(MirrorBlockJob *s, + int64_t offset, + int64_t bytes) +{ + return MIN(bytes, s->bdev_length - offset); +} + +/* Clip nb_sectors relative to sector_num to not exceed end-of-file */ static inline int mirror_clip_sectors(MirrorBlockJob *s, int64_t sector_num, int nb_sectors) @@ -184,44 +193,38 @@ static inline int mirror_clip_sectors(MirrorBlockJob *s, s->bdev_length / BDRV_SECTOR_SIZE - sector_num); } -/* Round sector_num and/or nb_sectors to target cluster if COW is needed, and - * return the offset of the adjusted tail sector against original. */ -static int mirror_cow_align(MirrorBlockJob *s, - int64_t *sector_num, - int *nb_sectors) +/* Round offset and/or bytes to target cluster if COW is needed, and + * return the offset of the adjusted tail against original. */ +static int mirror_cow_align(MirrorBlockJob *s, int64_t *offset, + unsigned int *bytes) { bool need_cow; int ret = 0; - int chunk_sectors = s->granularity >> BDRV_SECTOR_BITS; - int64_t align_sector_num = *sector_num; - int align_nb_sectors = *nb_sectors; - int max_sectors = chunk_sectors * s->max_iov; + int64_t align_offset = *offset; + unsigned int align_bytes = *bytes; + int max_bytes = s->granularity * s->max_iov; - need_cow = !test_bit(*sector_num / chunk_sectors, s->cow_bitmap); - need_cow |= !test_bit((*sector_num + *nb_sectors - 1) / chunk_sectors, + need_cow = !test_bit(*offset / s->granularity, s->cow_bitmap); + need_cow |= !test_bit((*offset + *bytes - 1) / s->granularity, s->cow_bitmap); if (need_cow) { - bdrv_round_sectors_to_clusters(blk_bs(s->target), *sector_num, - *nb_sectors, &align_sector_num, - &align_nb_sectors); + bdrv_round_to_clusters(blk_bs(s->target), *offset, *bytes, + &align_offset, &align_bytes); } - if (align_nb_sectors > max_sectors) { - align_nb_sectors = max_sectors; + if (align_bytes > max_bytes) { + align_bytes = max_bytes; if (need_cow) { - align_nb_sectors = QEMU_ALIGN_DOWN(align_nb_sectors, - s->target_cluster_size >> - BDRV_SECTOR_BITS); + align_bytes = QEMU_ALIGN_DOWN(align_bytes, s->target_cluster_size); } } - /* Clipping may result in align_nb_sectors unaligned to chunk boundary, but + /* Clipping may result in align_bytes unaligned to chunk boundary, but * that doesn't matter because it's already the end of source image. */ - align_nb_sectors = mirror_clip_sectors(s, align_sector_num, - align_nb_sectors); + align_bytes = mirror_clip_bytes(s, align_offset, align_bytes); - ret = align_sector_num + align_nb_sectors - (*sector_num + *nb_sectors); - *sector_num = align_sector_num; - *nb_sectors = align_nb_sectors; + ret = align_offset + align_bytes - (*offset + *bytes); + *offset = align_offset; + *bytes = align_bytes; assert(ret >= 0); return ret; } @@ -257,10 +260,18 @@ static int mirror_do_read(MirrorBlockJob *s, int64_t sector_num, nb_sectors = MIN(s->buf_size >> BDRV_SECTOR_BITS, nb_sectors); nb_sectors = MIN(max_sectors, nb_sectors); assert(nb_sectors); + assert(nb_sectors < BDRV_REQUEST_MAX_SECTORS); ret = nb_sectors; if (s->cow_bitmap) { - ret += mirror_cow_align(s, §or_num, &nb_sectors); + int64_t offset = sector_num * BDRV_SECTOR_SIZE; + unsigned int bytes = nb_sectors * BDRV_SECTOR_SIZE; + int gap; + + gap = mirror_cow_align(s, &offset, &bytes); + sector_num = offset / BDRV_SECTOR_SIZE; + nb_sectors = bytes / BDRV_SECTOR_SIZE; + ret += gap / BDRV_SECTOR_SIZE; } assert(nb_sectors << BDRV_SECTOR_BITS <= s->buf_size); /* The sector range must meet granularity because: -- cgit v1.2.3